Allison was founded in 1909, and is today known as Allison Transmission. Allison was owned by General Motors up until 2007, when it was sold to a private equity company. This company then took Allison public on the New York Stock Exchange in 2012. Today, Allison is the dominant player in the commercial truck industry when it comes to full automatic transmissions. While Eaton, Freightliner, Volvo, and others have developed “automated” transmissions, Allison is the only fully automatic transmission on the market. Through the years, Allison has developed new iterations of their technology, which they call “Generations”. We get quite a few people asking us which years are which generations so that they can source the proper Allison diagnostic software, and the proper Allison repair information.

ALLISON WTEC II

Lets start with the oldest Allison Transmission configurations, the “WTEC”. If your commercial truck, RV, or equipment is 1998 or older, it probably has a WTEC II Transmission. For a WTEC II, there is no diagnostic software or computer you can purchase. All of the electronics was done with the old school ProLink 9000. However, you can retrieve codes from the the shift selector. Listed below are the two types of shift selectors you may see on an Allison WTECII Transmission.

Depending on which type you have, you will be able to pull transmission codes.For a push button selector style, press the UP and DOWN arrow at the same time.
For a lever shift selector style, press the DISPLAY MODE button on the device.If the vehicle has an oil level sensor, the fluid level will be displayed first. The diagnostic code is displayed by either pressure the up and down arrow buttons, or the display model button depending on which style you have. Your system will now display a set of three codes, and then repeat.

Code Position (“d1” means it is the first code, “d2” the second, and so on)

Main Code (This will be a two-digit number)

Sub Code (This again will be a two-digit number)

If the code is active, the “mode on” indicator will be illuminated.To help troubleshoot your codes, we are pleased to give you the entire WTEC II Troubleshooting Manual. Just fill out the form and it will be emailed to you.

ALLISON WTEC III (GENERATION 3)

Introduced in January 1998, the WTEC III (Also known as Generation 3 or “Gen 3”) replaced the WTEC II transmission controls. The Allison WTEC III brought us into the computer based diagnostic era, which means you can use a variety of diagnostic tools to connect to the Allison Transmissions to read codes, clear codes, perform diagnostic commands, and much. The controls for the Allison Transmissions also changed a little bit, as there are now several new styles as shown here.

The ability to read codes on the WTEC III is exactly the same as the WTEC II, so just scroll back up a little bit to get the exact procedure.Allison is also kind enough to give you a very nice PDF that gives this information, plus what all the codes mean. Just click here to download it: WTEC_III_DTC_List.pdf (2 downloads)

ALLISON GENERATION 4

Allison moved from the WTEC III (Also known as Gen 3) and introduced the Generation 4 (Gen 4) series. These transmissions started appear in trucks in the early 2000’s, around 2004/5 time frame. This new generation electronics added more sensors, more diagnostic capabilities, and more advanced configurations of the Allison Transmission product line. For generation 4, there are a couple different types of selectors you will see in your vehicle depending on if its is a 2009 and newer vehicle or not. There are several options for doing computer based diesel diagnostics on an Allison Transmission, such as Allison DOC, PF-Diagnose, TEXA, and many others.

To read codes on the newer Allison Gen 4 controls, the process is slightly different. To enter the diagnostic mode, it will depend on your type of shift selector. You do need to make sure your parking brake is applied first.If you have a PUSH BUTTON shift selector, press the UP and DOWN arrow five times.
If you have a LEVER shift selector, press the DIAGNOSTIC button five times.You are now in diagnostic mode, and it will cycle 4 codes at you.

Code Position (“d1” means first code, “d2” means second code, etc…)

The letter “P” or “U”

Main Code (This will be a two digit code)

Sub Code (This again will be a two digit alphanumeric code).

Your end result would look something like P0101, P0722, and so on.Allison is also kind enough to give you a very nice PDF that gives this information on the Generation 4, plus what all the codes mean. Go ahead and click this link to download it: Allison_Gen_4_DTC_Info.pdf (1 download)

ALLISON GENERATION 5

The Allison Gen 4 had a good run for about 7 years, and in 2012 Allison upgraded to the Generation 5 model, which is still used as of the time of this post. The 1000/2000 series made the switch first, and then 3000/4000 a couple years later in 2013 model year trucks There are several options for doing computer based diesel diagnostics on an Allison Transmission, such as Allison DOC, PF-Diagnose, TEXA, and many others.The Gen 5 Allison Transmission has really focused on “advanced prognostics”. They are focused on constantly monitoring operating parameters and then notifying the driver if there an issue. This includes oil life monitoring, filter life monitoring, and transmission health monitoring. The shift selectors have also been re-designed for this generation.

READING ALLISON GEN 5 CODES

To read codes on the newer Allison Gen 5 controls, it depends on if you have a press button or level style shift selected.For push button configurations, you press the UP and DOWN button at the same time.
For lever style configurations, simply press the MODE button.Allison also no longer provides descriptions or repair information for codes, which is a real bummer since they’ve done it for so long on other models. However, our DTC Solutions program has all the codes defined, plus repair information.RESETTING OIL LIFE MONITOR

The Gen 5 Allison Transmission have an oil life counter that will display a message when you are due to change your transmission oil. Once the oil has been changed, you can reset this without using any software. The process would be to select the following gears, while pausing for less then 3 seconds between each: N-D-N-D-N-R-N. The ignition must be “on” and engine not running.RESETTING OIL FILTER LIFE MONITOR

This transmission also has an “TRANS SERV” light that will display when the transmission oil filter needs to be replaced. Once replaced, shift the selector through the following gears, while pausing for less then 3 seconds between each: N-R-N-R-N-D-N. The ignition must be “on” and the engine not running.Generation 5 SummaryThere is a great video on YouTube that goes over all the new features of the Generation 5 Allison Transmission, so if you have time to watch it is well worth it.

SUMMARY

So there you have it, everything you care to know about Allison Transmissions, the history of the generations, how to read diagnostic trouble codes, and how to reset the oil and filter maintenance reminders. We appreciate any comments you can leave our way!